Saxitoxin (4), the paralytic agent of the California mussel Mytilus californianus, has long been recognized as one of the most toxic of the non-protein poisons known. More recently, however, this identical substance has become the object of intense medical interest. Thus, for example, a mixture of 4 and local anesthetics has been found to act synergistically to produce local anesthesia of long duration and low toxicity. Also, however, the toxin's physiological behavior makes it ideally suited for use as a probe of normal and afflicted tissue; and, in fact, 4 is an excellent tool for the study of synaptic and neuromuscular transmissions. Medical research now use this agent for the labelling, characterization and isolation of sodium channel components, and this latter discovery, in turn, has opened new avenues in the study of multiple sclerosis. Since only milligram quantities of 4 are available from the natural sources, any future studies in this area must be performed with synthetically derived material. In this proposal we outline a synthetic route to 4 which might allow for its preparation on multigram scales. A particularly attractive feature of this route is that it will allow for the selective introduction of labels at virtually any position of the molecule. An intermediate which should be directly convertable to 4 has already been prepared.